When you kill an NPC, it has a 5% chance (total) to drop one random item it is carrying. You can scan enemy NPCs to see what they have equipped; they will only drop an item they have equipped. It is generally assumed that the rest of its gear has been destroyed in combat.

It's roughly a 5% chance for creatures to drop a trophy or egg as well, but the larger the creature, the less likely the egg drop (0% chance for colossals).

or maybe ...just maybe, they found the factory that was producing all of the clones armor. I mean after all there was a grip of clones during the clone wars and I know many more cylinders ready to pump out more clones. So i am sure there was a warehouse some where full of clone armor. Maybe the bandits found it, raided and then decided to start a bunch of chaos in the galaxy. ;) just a thought

I don't believe the commando armor is restricted tech, there is no manufacturer listed. I inquired about it some time ago and was told it's something that was given out ages ago like the Mandalorian armor and cannot be made.